Angiogenesis is a feature of many diseases, including diabetic retinopathy, rheumatoid arthritis, atherogenesis, and the growth and metastasis of solid tumors and the prototype membranes of fibroblast growth factor (FGF) family are among the angiogenic growth factors that act directly on vascular cells to induce endothelial cell growth and migration. While the long-term goal of this application is to elucidate the signaling pathway initiated by FGF-1 which may ultimately reveal new strategies for antiangiogenic therapy, the immediate goal is to characterize the interaction of FGF receptor-1 (FGFR-10) with cortactin, a recently identified substrate for the FGF receptor, and src family and potential components of the FGF-1 induced signal transduction pathway. We will examine the function of these signaling modulators in FGF-1 mediated cell migration and proliferation in vitro and during angiogenesis in vivo. Specifically, we will identify the tyrosine residues in cortactin that are phosphorylated in response to FGF-1 using phosphopeptide mapping and phosphoamino acid analysis and the function of these sites will be studied by site-directed mutagenesis. It is anticipated that the results from these studies will provide criteria to define the authentic kinase(s) responsible for the tyrosine phosphorylation of cortactin. While our preliminary data suggest that both c-src and FGFR-1 are able to associate with cortactin, we will ascertain which is the more relevant kinase for cortactin by studying FGF-1-dependent tyrosine phosphorylation in vivo. Once the interrelationship among FGFR-1, cortactin and c-src are defined, we will further initiate deletion, site-directed mutagenesis studies to dissect the amino acid sequences involved in their association with the cytoskeleton and examine the mechanism responsible for the co- localization of cortactin and c-src with the cytoskeleton. Based on the results from these studies, we will attempt to design a series of dominant negative mutants that may interfere with the interactions between wild-type FGFR-1, c=-src and cortactin. These mutants will ultimately be exploited to study their biological roles in the FGF-1- mediated DNA synthesis and chemotaxis, and their potential as antiangiogenics in vivo.